The Port Authority is raising concerns that the law firm chosen to represent the Christie administration amid several investigations into the George Washington Bridge scandal has a conflict of interest.

Officials at the bi-state agency plan to send a letter to the firm Gibson, Dunn & Crutcher LLP expressing the concerns, which stem from the firm's work on a separate but potentially related case, said a knowledgeable source.

The firm is representing the Port Authority in a lawsuit lodged by the motorist group AAA over the agency's controversial toll hikes in 2011. Christie jointly steers the Port Authority.

The interests of the Port Authority and the Christie administration in both the toll hike lawsuit and the George Washington Bridge probes could diverge, presenting potential complications if the same law firm is representing both simultaneously, some within the Port Authority believe.

Court records show the George Washington Bridge controversy has already been raised in the AAA lawsuit since records surfaced last week linking the governor's office to the September lane closings that gridlocked Fort Lee for four days.

It's not clear when the Port Authority's letter will go out. The Port Authority has paid millions in billings by Gibson, Dunn & Crutcher attorneys, including Randy Mastro, who was also named yesterday as the Christie administration's attorney.

The motorist advocacy group argues in its lawsuit that the largest-ever toll hikes approved in 2011 are unreasonable because the agency is using some of the money to rebuild the World Trade Center.

In a court filing in federal court on Thursday, AAA New York's attorney claim that e-mails and messages that surfaced last week linking the governor's office to the George Washington Bridge closures are pertinent to the toll hike lawsuit.

"The communications are germane ... because they highlight the types of communications that can occur and have occurred between officials at the Port Authority and the New Jersey Governor's Office," attorney Kevin Mulry wrote. The AAA attorneys are pointing the explosive communications in an attempt to get the Port Authority to turn over documents it has claimed are priveleged.

The letter says that some of the messages that have surfaced are from former Deputy Executive Director Bill Baroni, Christie's previous top executive at the agency, who was deposed in the AAA lawsuit.

On Thursday, Christie's office said it was hiring lawyers at Gibson, Dunn & Crutcher, including Randy Mastro, who is also defending the Port Authority in the AAA lawsuit, to handle an internal review and to cooperate with a review by the U.S. Attorney's Office.

A spokeperson at the firm dismissed the concerns in a statement: "There is no conflict of interest in our firm's separate representation of the Port Authority and the Governor's Office in these separate matters."